The present invention relates to hand-operated surgical instruments, and more particularly to handles for such devices which provide a locking mechanism.
Surgical instruments have been devised wherein a tool, such as a biopsy forceps, grasping forceps or a retaining basket, is attached to the distal end of a guide wire with a handle connected to the guide wire's proximal end. The guide wire is inserted into the patient until the distal end is at the location where a biopsy sample or another object is to be removed. The tool then is operated via a control wire by manipulating the handle and the sample is removed by pulling the guide wire from the patient. For example, instruments of this kind are used to remove kidney stones.
U.S. Pat. No. 4,815,476 discloses a surgical instrument handle assembly having a slider which moves along a handle. The handle includes a ring through which a surgeon places a thumb and the slider has two rings which receive opposing fingers. The proximal end of the guide wire has a sheath that is attached to the handle and a control wire, which passes through the sheath, is connected to the slider. As the surgeon moves the slider with respect to the handle, the control wire moves longitudinally within the sheath. Movement of the slider in one direction causes the control wire to open the tool at the distal end of the guide wire, while opposite movement of the slider closes the tool.
Once the object has been grasped, it is desirable to lock the tool so that the object will not be dislodged during withdrawal from the patient's body. In the aforementioned patent, the control wire passed through a collet at the end of the handle to which the sheath was attached and the control wire then attached to the slider. A nut was tightened onto the collet to grasp the control wire preventing movement with respect to the sheath and thus lock the tool. This type of locking mechanism required the use of two hands to lock and unlock the instrument.
Furthermore, if the tool became caught while being extracted from the patient, further extraction often resulted in tearing of the tissue which was obstructing the tool. Therefore, it is desirable in such situations that the locking mechanism yield allowing the control wire to be pulled through the sheath upon continued attempts to extract the stuck tool.